To analyze and compare the sequence-specificity of DNA methylases controlled by several prokaryotes and lower eukaryotes. We will attempt to determine the molecular relationship of specificity sites for T2 dam+, T2 damh, M. Eco Pl and E. coli dam+; preliminary studies already suggest a relationship. We will attempt to determine whether DNA methylation may be involved in the radiation-sensitive phenotype of certain yeast mutants. The possible role of selective methylation/degradation of Chlamydomonas chloroplast DNA will be investigated to determine if "maternal inheritance" involves a DNA modification-restriction system (as found in prokaryotes).